Respuesta :
Answer:
a) 135 seconds
b) 3.71 standard deviations below the mean
c) Z = -3.71
d) Unusual
Step-by-step explanation:
Z-score:
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this question:
[tex]\mu = 245, \sigma = 36.4[/tex]
a. What is the difference between a duration time of 110 sec and the mean?
Duration of 110 seconds.
Mean of 245
245 - 110 = 135 seconds
b. How many standard deviations is that (the difference found in part (a))?
This is |Z|
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{110 - 245}{36.4}[/tex]
[tex]Z = -3.71[/tex]
[tex]|Z| = 3.71[/tex]
3.71 standard deviations below the mean
c. Convert the duration time of 110 sec to a z score
From b, Z = -3.71
d. If we consider "usual" duration times to be those that convert to z scores between -2 and 2, is a duration time of 110 sec usual or unusual?
Z is not in the interval of -2 and 2, so a duration time of 110 sec is unusual
